Polymers of monoethylenically unsaturated vinyl monomers have many uses because of their outstanding physical properties and their adaptability to economical manufacture. However, they have disadvantages which tend to limit their usefulness, such as susceptibility to action of solvents, lack of resistance to gasoline, oil, and grease, excessive flexibility and lack of resilience, and loss of dimensional stability and strength at relatively low temperature.
Various crosslinking techniques have been resorted to in trying to overcome the disadvantages mentioned that are associated with the conventional linear, two-dimensional form. Such techniques have generally not been completely practical because they sometimes necessitate the use of harsh reaction conditions and often result in degradation of the polymer, instability thereof to heat, and serious susceptibility to heat. The use of extraneous photosensitizers blended with the polymers encounter problems of compatibility, uniformity of distribution, volatility, toxicity, or exudation and migration of the additive, often resulting in premature and/or erratic crosslinking. It has been suggested in Tocker, U.S. Pat. No. 3,214,492 and Skoultchi, U.S. Pat. No. 3,429,852 to provide certain acetophenone or benzophenone derivatives having acryloxy or methacryloxy groups so that such compounds can be copolymerized with ethylene or with other vinyl monomers to provide copolymers that can be cured (i.e. crosslinked) after shaping by exposure to radiation. In general, however, these monomeric compounds are relatively expensive to manufacture.